The present invention relates to a method of using arc welding to butt-weld an end surface of a piece of bar steel such as a reinforcing bar to a flat surface such as that of a steel column to form a T-joint, and a device utilizing the same.
Recently, steel-reinforced concrete buildings and the like have become taller and larger, the numbers of reinforcing bars used in these buildings have increased correspondingly, and it has also become common to use steel bars of larger diameters and longer lengths therefor.
When a reinforcing bar is welded to a surface such as a steel column, an end surface of the reinforcing bar is butt-welded to a side surface (either flat or curved) of the steel column. To enable this welding when using conventional methods, a planar steel plate 2 is temporarily welded as shown in FIG. 14 to a side surface of a vertically erected steel column 1, an end portion that is an oblique tip surface 4 of a reinforcing bar 3 is mounted so it is held by the steel plate 2, and weld beads W are built up by arc-welding between the oblique tip surface 4 and the steel column 1 to weld together the reinforcing bar 3 and the steel column 1. In this case, a side surface of the reinforcing bar 3 can also be welded to the steel plate 2.
As a result of the use of this welding method, the angle .theta. between the steel column 1 and the steel bar 3 is 90.degree. and if, for example, a floor surface is formed on top of the reinforcing bar 3, the reinforcing bar 3 acts as a strengthener for the floor surface and provides resistance to bending and shear stresses due to floor loading. Note that the angle .zeta. can be varied within the range of 45.degree. to 90.degree..
When it becomes necessary to weld a reinforcing bar to an existing steel column during the enlargement or remodeling of a concrete building on the spot, a hole is driven through a prescribed position of the steel column (such as a side surface thereof), the end portion of the reinforcing bar is inserted into this hole and is held thereby, and the portion of the hole is welded in order to weld the reinforcing bar and the steel column together into a single structure.
As an alternative method, a threaded hole could also be drilled in the side surface of the steel column, and a male thread cut into the end of the reinforcing bar could be engaged with the threaded hole to fix the bar to the column without welding.
However, when the steel plate 2 is temporarily welded the side surface of the steel column 1 and the reinforcing bar 3 is held thereon for arc-welding, as described in the first method above, the on-site work required for this temporary welding of the steel plate 2 must be added, and as such buildings become taller and larger, the number of places where reinforcing bars are welded also increases, so that this work become even less simple. Another problem involves the way in which the end of the reinforcing bar 3 becomes molten and starts to flow during the welding of the oblique tip surface 4 of the reinforcing bar 3 to the steel column 1, so that the thickness of the end of the reinforcing bar is reduced and thus it is difficult to guarantee the initially predicted strength thereof.
The second method, in which a hole is formed in the steel column and the reinforcing bar is inserted therein to be held for welding, also causes problems in that the thicknesses of the columns increase as buildings become bigger, so that it not only becomes extremely difficult to drill such holes on site, but also cross-sectional damage to the steel columns can occur and this can result in strength problems.